What are the manifestations of rich and lean mixture ratios?
2 Answers
Phenomena of excessively rich or lean air-fuel mixture are as follows: 1. Lean mixture symptoms: Carburetor backfire, difficult starting, engine overheating, detonation in cylinders, power loss (these symptoms improve when choke is closed), knocking sound during acceleration, unstable idle speed prone to stalling, very white spark plugs. 2. Rich mixture symptoms: Black smoke exhaust with possible oil droplets, engine overheating, insufficient power, unstable operation, increased fuel consumption, muffled engine sound, weak acceleration, unstable idle speed, severely blackened and carbon-fouled spark plugs. 3. Rich mixture: When the excess air coefficient is between 0.85-0.95, flame propagation speed reaches maximum, enabling fastest combustion that achieves peak cylinder pressure and temperature in shortest time with minimal heat loss, producing maximum work output. Since slightly more fuel is supplied than required for complete combustion at fixed air volume, oxygen utilization improves, increasing combustion product molecules and gas pressure - thus enabling the engine to deliver maximum power. This mixture is called the maximum power mixture.
The air-fuel mixture ratio refers to the proportion of air to fuel in a car engine. When the mixture is too rich, there's too much fuel, which manifests as significantly increased fuel consumption—for example, normal consumption of 8 liters per 100 kilometers suddenly rises to 12 liters. Black smoke comes out of the exhaust, especially noticeable during cold starts, accompanied by a strong gasoline smell. The engine runs unevenly, idles roughly, and may even stall. A rich mixture is often caused by faulty fuel injectors or sensors like the oxygen sensor. On the other hand, a lean mixture means too much air, resulting in weak performance, poor acceleration when pressing the gas pedal, and noticeable struggles when climbing hills. The exhaust may backfire with popping sounds, resembling pinging or knocking. The engine also tends to overheat, with the coolant temperature light frequently turning on. If these issues aren't resolved, they can damage the engine's lifespan over time. It's recommended to use diagnostic tools to check for trouble codes and address them promptly.
